Field of the Invention
The present invention concerns wireless communications, and more specifically, to methods for performing communication by user equipments (UEs) in a wireless communication system where a plurality of small cells are arranged and UEs using the methods.
Related Art
3GPP (3rd Generation Partnership Project) TS (Technical Specification) Release 8-based LTE (long term evolution) is a mobile communication standard.
Currently, 3GPP LTE-A (advanced), an evolution version of 3GPP LTE, is being standardized. A technique adopted by 3GPP LTE-A is carrier aggregation.
Carrier aggregation uses multiple component carriers. Each component carrier is defined with a center frequency and a bandwidth. One downlink component carrier or a pair of uplink component carrier and downlink component carrier corresponds to one cell. A user equipment (UE) receiving services using a plurality of downlink component carriers may be said to receive services from a plurality of serving cells. Conventionally, carrier aggregation presumes that a single base station located in the same site assign a plurality of cells, i.e., a plurality of frequency bands, to the UE and support the UE.
Meanwhile, in the next-generation wireless communication system, a plurality of base stations present in different sites may be assigned to a single UE to support the UE. Each base station may use different cells, i.e., different frequency bands, and a particular base station may be in the relationship of controlling the other base stations.
In such system, each base station may operate in an ON or OFF state. A need exists for a method for effectively signaling the UE with the ON/OFF state of each base station. Further, it needs to be specified how the UE receiving the signal is to operate.